What if polar bears meet grizzly bears

When grizzlies hang out with polar bears - and climate change is to blame

In Alaska they are mostly just casually called pizzlies or grolars: Both names stand for a mixture of polar bears and grizzlies. Such mixed forms or hybrids have sporadically occurred in zoos, but also in nature. But now their number is increasing. According to researchers, this is due to warmer temperatures due to climate change.

"The habitats of polar bears and grizzlies overlap more and more," explains Andrew Derocher. The biology professor at the University of Alberta (Canada) has been researching arctic bears for 30 years. "We don't know exactly how many hybrids there are at the moment. We only have eight genetically determined so far. But I estimate that several thousand polar bears live in regions of Alaska and Canada where they can meet grizzlies." There could also be overlaps in Russia.

The DNA cocktails examined show that until now it has always been male grizzly bears that mate with female polar bears - never the other way around. This is because the females of both species tend to stay true to their home region, while grizzly males in particular like to expand their territory. The Derocher researchers found not only 50:50 hybrids in arctic latitudes, but also those with three-quarters of grizzly DNA. From this it can be concluded that pizzlies can reproduce. For a long time, a cross between the two races was unthinkable due to their different living conditions. When they met, it was natural enemies.

"We don't know exactly how the hybrids live, but grizzlies and polar bears are dramatically different species," emphasizes Derocher. Polar bears need the ice, where they find walruses and seals for food, they do not hibernate and do not penetrate south into the tundra. According to WWF, there are currently an estimated 20,000 to 25,000 animals worldwide.

Grizzlies, on the other hand, do not usually frolic north of the tree line because it is too cold in the permafrost and hunting for land animals in the ice is too difficult. But with the rising temperatures, the tree line is also shifting to the north. "Hybrids probably live more like grizzlies," estimates Derocher. This is indicated by the first documented case in 2006 where a pizzly hunted land animals. "That was all the more surprising since he had spent two and a half years with his mother polar bear."

The scientific director of the organization "Polar Bears International", Steven Amstrup, emphasizes that hybrids like the Pizzlys are by no means genetic anomalies, but rather occur among closely related species. There is the coywolf - a mixture of coyote, dog and wolf - as well as the mix of bobcat and lynx.

In the case of the bears, however, the question is who will continue to spread and possibly prevail. "Hunting is not the main risk for polar bears," says Derocher. "We are concerned about the hunting quotas, toxic chemicals, oil spills and shipping, but these are small compared to the loss of habitat due to climate change." The grizzly advance northward is one of them. Derocher estimates that when the first female grizzly mate with male polar bears it will be the beginning of the end of the great whites.

By the middle of this century, experts predict that two-thirds of today's polar bear populations will have disappeared. There will not be enough ice in southern Alaska. Polar bears will only be allowed to live in the highest parts of the Canadian Archipelago and in northern Greenland. According to Derocher, the crucial question will then be: "Is there enough space for animals there to preserve the species until the planet cools down again?"